1. Field of the Invention
The present invention relates to a flexible connection substrate and a folding electronic apparatus, and more particularly to a flexible connection substrate that is ideally used in a folding portable terminal such as a folding portable telephone, and to a folding electronic apparatus that uses this flexible connection substrate.
2. Description of the Related Art
In recent years, portable telephones have come into wide use, and among these devices, folding portable telephones in particular are in wide use. A folding portable telephone includes an upper case and a lower case that are freely rotatably linked together by a hinge. The upper case has a display unit, a speaker for producing sound from the receiver and from received sound, and a first circuit substrate for these components. The lower case has an operation part that includes a plurality of keys for input, a microphone for collecting transmission sound, and a second circuit substrate for these components. The first circuit substrate and the second circuit substrate are connected to each other by a flexible connection substrate. During use, a folding portable telephone is placed in an opened state in which the upper case and the lower case are opened to a prescribed angle with the hinge as the fulcrum, and when not in use, is placed in a closed state (folded state) in which the two cases are placed in substantially close contact with each other.
The flexible connection substrate includes, for example: a belt-like flexible base material; printed wiring patterns such as signal lines and a ground pattern (GND signal lines) that are formed on the base material; and connector terminals that are provided at the two ends of the base material. The connector terminals are connected to the first circuit substrate and the second circuit substrate, respectively. In this way, the same signals are transmitted to the first circuit substrate and the second circuit substrate by way of the flexible connection substrate. At this time, any voltage difference that occurs between the GND voltage of the first circuit substrate and the GND voltage of the second circuit substrate is not desirable from the standpoint of the electrical design, and the width and length of the ground pattern that is formed on the flexible connection substrate are therefore designed such that a difference in voltage does not occur. However, considerations relating to the folding construction and to more compact construction have limited the width and length of the ground pattern in a folding portable telephone, raising problems of reliability regarding the secure connection of the circuit substrates.
Japanese Patent Laid-Open Publication No. 2003-110210 discloses a flexible connection substrate in which ground patterns are formed on a first and second connection ends and a connection is realized between these ground patterns by jumper wires that are independent of the printed wiring pattern of the printed wiring board. By means of this configuration, the ground patterns of the printed wiring pattern are connected by means of the jumper wires, whereby the difference in ground voltage between the circuit substrates can be set to a desired value.
In this configuration, the jumper wires are routed through the hinge. There are now folding portable telephones having a variety of hinge constructions, including folding portable telephones in which the routing of jumper wires inside the hinge is extremely problematic. In addition, connection by jumper wires is not preferable from the standpoint of manufacture due to limitations in connection methods, such as soldering.
Japanese Patent Laid-Open Publication No. 2004-104528 discloses a radio device in which wiring (signal lines) other than ground lines of a first circuit substrate and a second circuit substrate are mutually connected by a first flexible connection substrate, and the ground lines of each of the first circuit substrate and second circuit substrate are connected by a second flexible connection substrate. However, the first and second flexible connection substrates are constructions that are completely independent of each other, and this publication discloses nothing more than the independent connection of signal lines and ground lines. In this radio device, moreover, no consideration is given to a construction for routing a flexible connection substrate in the hinge so as not to interfere with the operation of two cases that are linked together by a hinge. Further, the radio device gives no consideration to shielding the noise that is generated from the first flexible connection substrate for connecting signal lines.